A high resolution electrophoretic technique was combined with immunofixation electrophoresis and applied in the study of serum proteins of myeloma and lymphoma cases. By this technique an immunoglobulin band was detected and identified in the serum of an occult myeloma patient. This finding is useful because early detection of a malignant process is desirable for early therapeutic intervention. An IgM Cretaceous band was found in the serum of lymphoma patients. The presence, disappearance and reappearance of this band was correlated with the clinical course of this disease, thus serving as a biochemical marker of the malignant process.